#include<bits/stdc++.h>
using namespace std;

#define RASHED ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl "\n"
#define int long long int

#define show(x) cout << #x << " = " << x << endl
#define inf (int)1e17
#define maxn 100010

#define F first
#define S second

bool solve(int tc) {
    int n;cin>>n;
    if(n>50)return false;
    return true;
}
signed main() {
    RASHED
    int TC = 1;
    ///cin>>TC;
    for(int i=1; i<=TC; i++)cout<<(solve(i)?"YES":"NO")<<endl;
    return 0;
}
/**
CASES:

*/